1. Field of the Invention
The present invention relates to novel lincomycin derivatives having antimicrobial activity or their pharmacologically acceptable salts thereof. The present invention also relates to antimicrobial agents comprising the compounds as active ingredient.
2. Related Art
Various compounds have hitherto been reported as lincomycin derivatives having antimicrobial activity. It is also disclosed that compounds having a structure similar to the compounds according to the present invention have antimicrobial activity. See, for example, (1) U.S. Pat. No. 3,915,954, (2) U.S. Pat. No. 3,870,699, (3) U.S. Pat. No. 3,767,649, (4) German Patent Laid-Open No. 2229950, (5) U.S. Pat. No. 3,689,474, (6) U.S. Pat. No. 3,544,551, (7) International Publication WO 2005/012320, (8) J. Antibiotics, 49, (1996), 941, and (9) Structure-Activity Relationships among the semisynthetic antibiotics, 601-651.
The compounds described in these documents, however, are ineffective against resistant pneumococci which have recently posed a clinical problem. Accordingly, the development of antimicrobial agents comprising lincomycin derivatives which are also effective against resistant pneumococci has been desired.